A belt conveyor for transporting aggregate material is generally a trough-type conveyor which may be loaded at the tail section of the conveyor and at any point along its length. Belt conveyors are provided with conveyor belt covering skirts which direct the material being loaded to a central portion of the conveyor belt. The conveyor belt tends to shift laterally from its centered position as it is driven by the drive pulleys on the idler pulleys. This lateral shifting leads to off-centered loading onto the conveyor belt. This occurs because the conveyor belt cover skirts are fixed and stationary. This lateral shifting is sufficient to expose the idler pulleys and the drive pulleys such that the material being loaded can miss the conveyor belt and foul these mechanisms in the conveyor. U.S. Pat. No. 5,458,230, which is incorporated herein by reference, discloses a system with a carriage having side loading skirts which is transversely shiftable in response to lateral shifting of a conveyor belt so that the loading skirts direct material to a central portion of the belt even if the belt shifts transversely. However, the carriage uses rollers provided with a V-shaped rolling surface which rolls on a V-shaped track. The lateral force that the conveyor belt imparts on the V-shaped roller creates friction to movement and frequent derailing of the carriage from the track. The roller and track arrangement also is frequently fouled with load material debris due to its open design. In order to allow for maximum loading of the conveyor belt, what is needed is a center loading assembly that is capable of operating in a circular path, to operate with a conveyor belt that is troughed up to 80 degrees.